Electromagnetic sound-reproducing device



June 2, 1942. e. BEHRE ,2

ELECTROMAGNETIC SOUND-REPRODUCING DEVICE Filed March 29, 1940 Patented June 2, 1942 than Giinther Bohr-e, r

. a my, assignor to Q.

Lorena icngeselisohatt, lBer-Telhot,

Ge rm. .1.

Application i7 1' Ev fiflmn r.

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The invention relates to sound-reproducing devices of the kind having a wire, tape or plate as record carrier on which the sound tobe reproduced is magnetically impressed.

The hitherto known methods of sound reproduction fail to produce tones of the same perwith the record carrier low frequencies are well reproduced tree from any distortion, whereas the reproduction of high frequencies is distorted.

With two magnet poles used for reproduction high frequencies are better reproduced than low frequencies w ch are distorted.

In order to-avoid these disadvantages the invention provides for reproducing the low irequencies mainly by means of one is and the high frequencies .mainly by two pd es. To such end in a preferred embodiment of the invention a filter circuit including a condenser and a choke coil is employed whereby no switchingover from the one to. the two pole arrangement be necessary.

Three embodiments are diagrammatically represented in Figs. 1, 2 and 3 the drawing.

I and 2 denote magnet poles which belong to coils 3, 4 of a so-called talking head. These coils are interconnected in series. Between the poles i, 2 the record carrier 5 extends. which may be a wire, a tape or a plate. In the lead to coil 3 a condenser 6 is included. Coil 3 and condenser 6 are bridged over by a choke coil I.

Owing to this "arrangement the coil 3 will be inefiective in the case of low frequencies, since condenser 6 acts as a high resistance with respect to them. As regards high frequencies however, the coil I in its turn acts as a resistance, thus causing the current to pass through both coils 3, t.

It will be seen that a resistance may be arranged in lieu of coil 8. J

The invention is not restricted to the .device hereshown. For instance, the reproduction may be made by means of two talking heads one of which is unipolar in action while the other is bipolar. Furthermore, two talking heads may be arranged to operate each in bipolar fashion, one oi them be ng adapted to reproduce high frefection throughout the entire voice frequency range. When only one magnet pole' cooperates quencies while the other is suitable for the reproduction of low frequencies. In such structures the talking heads themselves constitute the filter circuit.

According to the embodiment shown in Fig. 2 one reproducing head is unipolar and consequently favors the low frequencies, whereas the other is bipolar and responds better to the high frequencies. In Fig. 2, numeral I represents the sound carrier. 2', 3' are the poles and d, 5' the windings oi the bipolar reproducing head, whereas the unipolar reproducing head consists oi pole t with winding l. The windings oi the two reproducing heads. are connected in parallel. Another embodiment of the invention is shown in Fig. 3, using two bipolar reproducing heads for the pick-up. Since as stated above, a bipolar reproducing head reproduces best the high frequencies. an air-gap between pole and sound carrier is provided tor in one of the reproducing heads, whereby the low frequencies are favored in the pick-up. Fig. 3 represents the sound carrier 6'', the poles2", 3" with winding d", B", of one of the bipolar reproducing heads and poles t", l" with windings 8", 9" of the other bipolar reproducing head The two reproducing heads are connected in parallel.

:What is claimed is: I l

1. In a sound reproducing device for magnetic sound carriers, a pick-up comprising at least two opposed poles, and means including a filter circuit for rendering part of said pick-up ef fective to reproduce only low frequencies.

2. In a sound reproducing device for magnetic sound carriers, a pick-up comprising two opposed poles, coils for said poles, a connection'between one of the terminals of said coils, a condenser having one plate connected with the other terminal of one coil, and an impedance between the first mentioned connection and the other plate of said condenser. H

3. In a sound reproducing device for magnetic sound carriers, a pick-up comprising two opposed poles .and a single pole, coils for said two poles connected in series, and a coil for said single pole bridged across said coils.

iiN'rHER BEHRE. 

